The complaint with plastic bowls, the biggest complaint is that plastic bowls will absorb the fat in dog food- just like plastic does with speghetti, meat etc.
The biggest problem with ceremic bowls is that dog bowls are not made for humans. Even glazes on the bowls if made outside the US and Canada ( china being the biggest offender) not only will wear off, but the glaze itsself is not made for people. I am afraid many Asian countries have little regard for dogs and cats obviously.
The idea of painted meaning colors is what amazed me the most. I use to do ceremics and really it makes sense. The paints do have lead in them, and even recommended the use of gloves in applying most colors. Now I know why...
When we were having brands of dog foods tested for ethoxyquin, I also sent in two of my oldest bowls- they were a thick plastic- they came back " rancid on fat content". I use stainless steel bowls and have for years, but I always wash my bowls after they eat. This was recommended because I feed raw, and done more so for my protection.